The anatomist's vade mecum : a system of human anatomy / by Erasmus Wilson ; with 200 illustrations by Bagg.

  • William James Erasmus Wilson
Date:
1847
Catalogue details

Licence: Public Domain Mark

Credit: The anatomist's vade mecum : a system of human anatomy / by Erasmus Wilson ; with 200 illustrations by Bagg. Source: Wellcome Collection.

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    the ovum itself originally presented this simple form, and the embryo at an early period is wholl}' composed of such nucleated cells. In their relation to each other, cells may be isolated and independent, as is exemplified in the corpuscles of the blood, chyle, and lymph ; secondly, they may cohere by their surfaces and borders, as in the epiderma and epithelium; thirdly, they may be connected by an intermediate substance, which is then termed intercellular, as in cartilage and bone; and, fourthly, they may unite with each other in rows, and upon the removal, by liquefaction, of the adherent surfaces, be converted into hollow tubuli. In the latter mode capillary vessels are formed, as also are the tubuli of nerve and muscular fibre. One of the properties of cells may also be adverted to in this place; it is that of reproducing similar cells in their interior. In this case the nucleoli become the nuclei of the secondary cells, and as the latter increase in size, the membrane of the primary or parent cell is lost. Bone, in its earliest stage, is composed of an assemblage of these minute cells, which are soft and transparent, and are disposed within the embryo in the site of the future skeleton. From the resemblance which the soft tissue bears to jelly, this has been termed gelatinous stage of osteo-genesis. As development advances, the cells, heretofore loosely collected together, become separated by the interposition of a transparent intercellular substance, which is at first fluid, but gradually becomes hard and condensed. The cartilaginous stage of osteo-genesis is now established, and cartilage is shewn to consist of a transparent matrix, having minute cells disseminated at pretty equal distances and without order through its structure. Coincident with the formation of cartilage is the development of vascular canals in its substance, the canals being formed by the union of the cells in rows, and the subse- quent liquefaction of the adhering surfaces. The change which next ensues is the concentration of the vascular canals towards some one point; for example, the centre of the shaft in a long, or the mid-point of a flat bone, and here i]\epuncturri ossificationis, or centre of ossifica- tion, is established. What determines the vascular concentration now alluded to, is a question not easily solved, but that it takes place is certain, and the vascular punctum is the most easily demonstrable of all the phenomena of ossification. During the formation of the punctum ossificationis, changes begin to be apparent in the cartilage cells. Originally they are simple nucleated iiTiun) ’anSo i^ich in diameter), having a rounded form. As growth proceeds, they become elongated in their figure, and it is then perceived that each cell contjiins two and often three nucleoli, around which smaller cells are in progress of formation. If we ex- amine them nearer to the punctum ossificationis, we find that the young or secondary cells have each attained the size of the parent cell of an inch), the membrane of the parent cell has disappeared, and the young cells are separated to a short distance by freshly effused inter- cellular substance. Nearer still to the punctum ossificationis a more remarkable change has ensued, the energy of cellule reproduction has